1. Field of the Invention
An endless belt sander comprising an arrangement of pulleys to control an endless belt which partially surrounds a workpiece of substantial diameter.
2. Description of the Prior Art
There has long existed the problem of not having a sufficient means of sanding or polishing surfaces of limited access with mechanical devices and the exertion of excess manual effort. An example of such a situation is the difficulty encountered in trying to sand the entire circumference of stair bannisters from the stair side. A further example would be chair rungs commonly found in the arrangement of many designs of chairs. Furthermore, there are innumerable instances where surfaces to be sanded or polished are inaccessible by the devices found in the prior art where the access openings to that object which is to be sanded are smaller than the apparatus that must be extended within. Quite often the devices of the prior art have rollers to control the polishing or sanding belt which have rollers that must be extended within such openings but unfortunately have diameters which are of such dimensions that they will not fit within such openings.
The sanders commonly found in the prior art are not configured so as to allow the belt to engage a substantial portion of a curved surface. Commonly such sander assemblies have a belt tightly wrapped around a configuration of pulleys or rollers so that they form a substantially flat plane in which to engage a curved surface. This allows for only a small portion of that curved surface to be sanded in any short period of engagement. There is a need in this field to have a sander that is capable of wrapping around a substantial portion of a curved or circular surface so as to complete the sanding or polishing process in a uniform manner without having to have a series of rearrangement of the point of engagement of the sanding device with the workpiece. Furthermore, the requirement of having the belt tightly wrapped around an arrangement of pulleys or rollers results in the length of the belt having to be relatively short.
The devices of the prior art commonly drive the belt on the pulleys without belt slippage by having the belt tightly wrapped around an arrangement of pulleys or rollers. This method of insuring proper transfer of torque without belt slippage requires tension of the belt around the pulleys. This is commonly accomplished by having at least one pulley on an adjustable extended arm which can tighten the tension in the belt. Of course, such an arrangement totally prevents the wrapping of an originally slacked belt around a workpiece of substantial diameter or disposed in an area of limited access.
Likewise, any such device overcoming the above problems should also be portable enough to easily be taken to the jobsite without having to remove the object to be sanded.
Thus, it is apparent that a real need exists for a polishing or sanding device that is capable of being used in places of limited access, having a belt of unlimited length and width, engaging substantial portions of curved surfaces and objects of large diameters, of transferring power without belt slippage having a rather slack belt arrangement, and at the same time being portable.